discrete math, asap please

4. Using the hexadecimal symbols described in question \# 4 on page 68 of DMOI, answer the following questions about building 40 -bit hex strings. Show all your answers using exponents such as 911. 1. How many strings can be made with the left most digit being a numeral? 2. How many strings alternate between letters (AF) and numerals (09) ? Example: A1B2A3B4 is such pattern. 3. How many hex strings can be made so that no letters appear before numerals? hexadecimal We usually write numbers in decimal form (or base 10), meaning numbers are composed using 10 different "digits" {0,1,,9}. Sometimes though it is useful to write numbers hexadecimal or base 16. Now there are 16 distinct digits that can be used to form numbers: {0,1,,9,A,B,C,D,E,F}. So for example, a 3 digit hexadecimal number might be 2B8